If you want to reset your Firefox preferences, this article provides instructions on how to reset them through Safe Mode.

To reset preferences:

At the top of the Firefox window, click the Firefox button, go over to the Help menuOn the menu bar, click the Help menuAt the top of the Firefox window, click the Help menu and select Restart with Add-ons Disabled.... Firefox will start up with the Firefox Safe Mode dialog.

Note: You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.holding down the option key while starting Firefox.quitting Firefox and then going to your Terminal and running: firefox -safe-modeYou may need to specify the Firefox installation path (e.g. /usr/lib/firefox)

Click the menu button
, click help
and select Restart with Add-ons Disabled.... Firefox will start up with the Firefox Safe Mode dialog.

Note: You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.holding down the option key while starting Firefox.quitting Firefox and then going to your Terminal and running: firefox -safe-modeYou may need to specify the Firefox installation path (e.g. /usr/lib/firefox)

To reset your user preferences, click to put a check mark by Reset all user preferences to Firefox defaults.